Crotalus oreganus oreganus near its southern range limit is variable in appearance, often looking very much like C. o. lutosus. An example is the Kern County snake seen in the row above. Identification of rattlesnakes found in this region can be confusing and open to debate. Some of these controversies should be resolved when the results of further studies on these species are published.

According to Robert Hansen who has studied the area in depth: "Among populations of "oreganus" inhabiting arid landscapes near their southern range limits (e.g., southern San Joaquin Valley, Carrizo Plain), there is a tendency toward small size, light ground color, and reduced dorsal blotch size...features that cause these snakes to superficially resemble lutosus."..."The southern extent of the range of lutosus in eastern California (e.g., the Mono/Inyo counties region) has been mapped in reasonable detail, and thus far, there are no known instances where the ranges of oreganus and lutosus come into contact.
However, farther north, where the Sierra Nevada crest is much lower and the potential for populations of oreganus and lutosus to meet is likely greater, careful field studies are lacking. Ultimately, reliance on features of coloration and pattern to distinguish one form from the other in areas of potential contact is not advised."

Rattlesnakes are important members of the natural community. They will not attack, but if disturbed or cornered, they will defend themselves. Reasonable watchfulness should be sufficient to avoid snakebite. Give them distance and respect.

"Rattlesnakes are also among the most reasonable forms of dangerous wildlife: their first line of defense is to remain motionless; if you surprise them or cut off their retreat, they offer an audio warning; if you get too close, they head for cover. Venom is intended for prey so they're reluctant to bite, and 25 to 50 percent of all bites are dry - no venom is injected."Leslie Anthony. Snakebit: Confessions of a Herpetologist. Greystone Books, 2008.

Rattlesnakes are the only kind of native California snakes that we typically refer to as poisonous, but actually, they are not poisonous they are venomous. A poisonous snake is one that is harmful to eat. A venomous snake injects dangerous venom into its victim.

Rattlesnake bites can be extremely dangerous, but rattlesnakes should not be characterized as agressive and vicious, striking and biting without provocation, as they are often shown in movies and TV shows. If rattlesnakes are given some space and some time to escape to a safe place, they will usually just crawl away as fast as possible and avoid confrontation. Rattlesnakes will not strike without a reason: they will strike at a potential meal and they will defend themselves from anything they perceive as dangerous. They avoid striking and biting because it uses up their valuable supply of venom which they need to kill and digest their food. Rattlesnakes are often portrayed with the body partly coiled, the tail rattling loudly, and the head raised up and ready to strike, but they do not need to coil this way to strike. This display is a warning not to come any closer. It's a defensive behavior that some rattlesnakes use when they sense that crawling away would put them in danger of attack.

Rattlesnaks do not always rattle. Often they will rattle loudly to warn potential enemies of their presence but they will often remain silent when they sense a threat, using their cryptic color and pattern to blend into their surroundings to hide from the threat. In this situation making noise risks advertising their presence. They also use their natural camouflage to hunt by sitting still and not rattling, trying to remain invisible as they wait for a warm-blooded prey animal to pass close enough for the snake to strike it.

Description

Dangerously Venomous(Commonly but inaccurately called "Poisonous.")

A bite from this snake can be very dangerous without immediate medical treatment. Treatment can require hospitalization and great expense.

Size

Adults of this species range from 15 - 65 inches long, ( 38 - 165 cm) but typically the adults seen are 3 - 4 feet long.
Newborns are around 10 inches long.

Appearance

A heavy-bodied pit viper, with a thin neck, a large triangular head, and a rattle on the end of the tail consisting of loose interlocking hollow segments.
Pupils are elliptical.
Scales are keeled.

Rattlesnakes are "pit vipers" which means they have two pits that are used to sense heat when hunting warm-blooded prey - with one pit on each side of the front of the head above the mouth.

Color and Pattern

The ground color is variable, matching the environment - pale grey, tan, light yellow, buff colored.
The back is marked with dark blotches with light centers, usually in the shape of bars or ovals, about as wide as the spaces between them.
The underside is pale, sometimes weakly mottled.
Two light stripes extend diagonally across the sides of the head, but they are sometimes faded and not evident.
The tail is barred, and without white rings.

Young

Young are born with a bright yellow tail with no rattle - just a single button which does not make a sound. They grow rattles and lose the yellow color as they age.
The pattern is brighter on juveniles than on adults.

Primarily nocturnal and crepuscular during periods of excessive daytime heat, but also active during daylight when the temperature is more moderate.
Not active during cooler periods in Winter.

Fangs and Venom

Rattlesnakes have long, hollow, movable fangs connected to venom glands. The fangs are replaced if broken. A snakes uses its fangs to inject a toxic venom which quickly immobilize its prey. A rattlesnake can control the amount of venom injected.

Bites that inject venom into humans are potentially dangerous without immediate medical treatment.
Sometimes a rattlesnake bites but does not inject venom. These are called "dry bites." A dry bite may still require medical attention.
Even a dead snake can bite and inject venom if the jaws open and close reflexively when they are touched.

A bite from any kind of rattlesnake of any age or any size should be treated as a serious medical emergency, but the bite of a juvenile rattlesnake is not more dangerous than the bite of an adult.
Experts disagree whether or not juvenile rattlesnake venom is more potent than adult rattlesnake venom, but this does not really make much difference in the severity of a bite.
While adult rattlesnakes can control the amount of venom they inject depending on their needs (small animals need less venom, a defensive or warning bite may need no venom, etc.), it is often assumed that juvenile rattlesnakes do not have the same ability and that they always inject the full amount of venom they have available. Some studies show this is not true.
There is also no proof that adult rattlesnakes are more likely than juveniles to bite without injecting venom when they are biting as a warning. Regardless of these things, adults have far more venom to inject than juveniles so the potential danger from the bite of an adult is significantly higher than the danger from the bite of a juvenile. Even when an adult does not inject the full amount of venom it has available, it most likely injects more venom than a juvenile would inject.

Sound - The Rattle

When alarmed, a rattlesnake shakes its tail back and forth. The movement rubs the rattle segments together producing a buzzing sound which serves as a warning. Juveniles are born with only a silent button at the end of the tail.

A new rattle segment is added each time the skin is shed, which can be more than one time per year.

Prey is found while the snake is actively moving, or by ambush, where the snake waits near lizard or rodent trails, striking at and releasing passing prey. The snake then follows the trail of the envenomated animal and swallows it whole.

Pits on the sides of the head sense heat. These heat sensors help the snake to locate prey by their warmth.

Rattlesnakes are ovoviparous. The mother keeps her fertilized eggs inside her body and gives birth to living young.
Breeding typically occurs in the spring. Males search extensively for females during the mating season.
Females probably start bearing young at three years of age and breed annually. (Klauber, 1982)
An average litter consists of 4 to 12 young which are born from August to October. (Stebbins & McGinnis, 2013)

Adult males engage in a ritual "Combat Dance" during the spring breeding season. Necks and forebodies are intertwined, with the stronger snake slamming the smaller one to the ground until the weaker snake leaves the area.
"...The presence of a female is not necessary to stimulate the males to dance." (Klauber, 1982)

This subspecies, Crotalus oreganus lutosus - Great Basin Rattlesnake, is found in California in the far northeastern corner and in a small region east of the Sierras near the Mono Lake area. It continues outside the state north into eastern Oregon, and east to western Utah, southern Idaho, most of Nevada, and barely into extreme northwestern Arizona.

The species Crotalus oreganus - Western Rattlesnake, occurs from the Pacific Coast of northern Baja California north through most of California except the southern deserts, through Oregon and eastern Washington into British Columbia, Canada, and east into Idaho, Nevada, Utah, southwestern Wyoming, western Colorado,and northern Arizona.

The taxonomy of Western Rattlesnakes is controversial with several different opinions, most of which recommend making the three subspecies found in California full species.

Some researchers still use the former species name Crotalus viridis and for them the subspecies represented on this page remains Crotalus viridis lutosus.

A study published in February 2016 used head shapes and genetic analyses to determine that there are 6 full species of western rattlesnakes found in the former Crotalus viridis complex and suggested the following names, with the three species found in California shown here at the top of the list.
If this taxonomy is accepted, the ranges and common names of western rattlesnakes found in California will remain the same, but they will be full species instead of subspecies.

Timber Rattlesnake (It is not uncommon for a rattlesnake found in a forested area in California
to be called a Timber Rattlesnake. The true Timber Rattlesnake (Crotalus horridus) is not found in California. It occurs from southeast Minnesota down to central Texas and east to northern Florida up to south-central New Hampshire.)

Crotalus - Greek - krotalon - a rattle - refers to the rattle on the tail
oreganus - belonging to the state of Oregon - referring to the type locality, "banks of Oregon or Columbia River" lutosus - Latin - muddy, full of mud - referring to the brownish dorsal color

Wright, Albert Hazen & Anna Allen Wright. Handbook of Snakes of the United States and Canada. Cornell University Press, 1957.

Conservation Status

The following status listings are copied from the April 2018 Special Animals List and the 2017 Endangered and Threatened Animals List, both of which are published by the California Department of Fish and Wildlife.

If no status is listed here, the animal is not included on either CDFW list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings.